Influence of vagal tone on rheology and transportability of canine tracheal mucus.

The influence of vagal tone on the rheology of tracheal mucus was studied in 6 conscious, tracheostomized dogs. Mucus was sampled via the tracheostomy with a cytology brush before and after administration of atropine. After vagal blockade, a clear decrease in the mucus collection rate was seen. The viscoelastic properties of the mucus were not altered by atropine when control elasticity was high, but when control elasticity was low, administration of atropine led to increased elasticity. In neither case was there a significant change in transportability of the mucus samples. The increase in elasticity from a small initial value was consistent with the blocking of moderate vagal activity, because administration of methacholine in the same group of dogs had been shown to cause a decrease in mucus elasticity.